Its important to remember that the vacuum lines on a 1980 are 30+ years old now
and ARE going to fail. The plastic has hardened and vibration will make them
break. Fixing vacuum issues isn't a "Today I work on it and it'll be good
forever" its going to be "I need to work on this every year from now until
forever" unless you replaced them all now...
A mityvac and the vacuum diagram is an investment into your future. Vacuum
troubleshooting isn't hard, you follow pull the block, pump it down (or try to
anyway) and follow the line to the offender.
For example:
Last fall I drove myself to the airport in my '78 240D, when I got there the
car wouldn't shut off. Manual transmissions are handy, step on the brake, pop
the clutch, problem solved. When I got back the problem hadn't magically fixed
itself but I did notice it wasn't an issue if the doors were unlocked. Hmm,
problem therefore MUST be in the door circuit, specifically the UNLOCK side of
the door circuit.
Theres a block of vacuum hoses under the driver's feet so I pull back the
carpet, start unplugging things and pumping down the mity vac and see what
happens. Some lock or unlock doors on the other side of the car (if one pulls
down but doesn't do anything release vacuum, change the lock state of the doors
(unlock or relock) and see what try again) and one unlocks the rear driver's
door but one doesn't seem to do anything and doesn't hold vacuum... Start
following that one, it goes under the driver's seat and I find a break where it
comes out. Find another in the door. Now the rear passenger's door unlocks and
relocks.
Start the car and verify function with engine vacuum, thats good AND the car
shuts off. Problem solved. Also replaced a 4 way adapter which makes the doors
unlock and relock faster and hold vacuum longer.
Theres more to be gained on this car (leaky old fittings) but I ran out of time
that day and its cold now so I'll work on it more in the spring.
-Curt
Date: Thu, 6 Jan 2011 16:51:27 +0000 (UTC)
From: roger...@comcast.net
To: mercedes@okiebenz.com
Subject: Re: [MBZ] 1980 300 SD vac lines again!
Message-ID:
<1187630811.867939.1294332687516.javamail.r...@sz0097a.westchester.pa.mail.comcast.net>
Content-Type: text/plain; charset=utf-8
If
you'll call me, I'll check the lines with you over the phone. I just
went through this with my Indie. Yes, instead of spending hours tracing
down lines with a Mity-vac, I let my Indie do it since he's trained on
what to look for, has the manuals, and I'm not. He found a leak in the
right rear door lock which was bleeding off vacuum...fixed that. Then
the cruise control was leaking vacuum...it don't work and I don't want
to use it...so he plugged that. Then we found a leak in the line from
the IP to the vacuum modulator on the tranny. I almost never found the
part number for the plastic cap (dealer and everyone on line wanted to
sell me the whole modulator valve for 70-90.00 instead of 14.00 for the
plastic cap). Fixed it and all is well.
As to the Hard Wired setup,
unless it works differently than what I've read, it won't fix your
blower problem. The 80 300SD with the servo has a vacuum pod under the
dash which controls the blower, except on defrost. Defrost over rides
because the windshield clearing is a driveability / safety issue. Hence,
if this pod is bad or any lines that can affect it (like my door lock
was doing), you won't get blower except for the defrost. I actually
replaced my blower motor, only to find that although it seemed like the
problem, it was really a vacuum problem from this control pod under the
dash.
Anyway, unless you want to buy a Mity-vac, buy the manuals,
and spend your spare time trying to figure which line you are really
tracing for vacuum, I'd recommend a good Indie. It's cheaper and quicker
in the long run. At least that has been my personal experience with my
two old 617s...others may have had different outcomes...over which I
have had no control. I like DIY also, but I realize my limitations and I
realize who is best at what tasks (me or my Indie) and act accordingly.
Best Wishes,
Roger Hale
Monroe, Ga.
770-267-1636
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